Great strides have been made in sequencing the full genomes of a number of eukaryotic organisms. In addition to the generally completed genomes of humans and model organisms such as Drosophila melanogaster and C. elegans, there will likely be genomic sequence data for a range of additional model organisms in the near future. While the sequencing technology itself has proven to be very powerful, there are still significant limitations in our ability to systematically characterize the biological roles of specific genes and predicted genes. One particularly useful tool would be a general technology to generate stocks carrying mutations in any genomic sequence of interest, and that could be applied to any experimental organism. Such methodology would be valuable for studies both of novel individual genes, and for the generation of genome-wide collections of mutant strains. Using Drosophila melanogaster as a model organism, my laboratory has been working on developing universal "reverse genetic" techniques for the targeted recovery of mutations. I propose here a novel approach for the in vivo generation and detection of small, intra-locus deletions for any known chromosomal sequence. Funds are requested to verify the feasibility and cost-effectiveness of the procedure. Future work will apply the technique to those Drosophila genes that are resistant to mutagenesis by current methods, and to generate mutations in a range of additional experimental organisms. The proposed work is high risk, because this particular approach has (to my knowledge) never been used for the purposes described here. However, this research could have a very high impact, providing a method to generate deletion mutations in any gene or chromosomal region for a wide range of organisms.